Transparent amorphous oxide semiconductor (TAOS) materials as typified by materials of In—Ga—Zn—O system (hereinafter, simply referred to as InGaZnO) exhibit higher mobility compared to a-Si, and therefore have been attracting much attention as materials that constitutes an active layer (channel layer) of a thin film transistor (TFT) for driving a large high-definition display. In particular, with regard to an InGaZnO-TFT (TAOS-TFT) deposited by vacuum deposition such as sputtering, technical consideration of issues relating to mass production has been advanced, and the technology has nearly reached a practical level (for example, see Japanese Patent Application Laid-Open (JP-A) No. 2010-21555).
On the other hand, as a technique for fabricating large-area TAOS-TFTs at low cost, research and development of a liquid phase method have been actively carried out (for example, see JP-A Nos. 2010-21333 and 2010-18479).